THE OPEN SKIES TREATY: OBSERVATION OVERFLIGHTS OF MILITARY ACTIVITIES
CRS Report for Congress
The Open Skies Treaty:
Observation Overflights of Military Activities
September 11, 2000
Specialist in National Defense
Foreign Affairs, Defense, and Trade Division
Congressional Research Service ˜ The Library of Congress
The Open Skies Treaty:
Observation Overflights of Military Activities
On March 24, 1992, the United States, Canada, and 22 European nations signed
the Treaty on Open Skies. The United States officially ratified the treaty on
November 3, 1993. The treaty has not yet entered into force, however, because
Russia and Belarus have not yet ratified it.
President Bush revived the Open Skies concept in May 1989. At the time, the
United States believed that the Open Skies concept would reduce the chances of
military confrontation and build confidence in Europe by providing participants with
the ability to collect information about the military forces and activities of others in
the treaty. In addition, even though the United States and Russia can collect this type
of information with sophisticated observation satellites, Open Skies observation flights
will provide nations who do not have their own satellites with a way to participate in
the data collection and confidence-building process.
The parties to the Treaty on Open Skies have agreed to permit unarmed aircraft
to conduct observation flights over their entire territories. The United States Air
Force has modified three C-135 aircraft for this purpose. Open Skies aircraft can be
equipped with four types of sensors: optical panoramic and framing cameras; video
cameras; infrared line-scanning devices; and sideways-looking synthetic aperture
radars. These sensors must be based on off-the-shelf technology that is available to
all participants in the treaty. The treaty includes quotas that specify maximum
numbers of observation flights that can occur within each nation each year and the
maximum number of observation flights each nation can conduct each year. For the
United States, these quotas are 42 flights per year; however, only 4 flights will occur
over U.S. territory in the first year that the treaty is in force. In addition, the United
States will conduct only 9 observation flights during the first year of treaty
implementation; 8 over Russia and Belarus and one, in conjunction with Canada, over
When the Senate reviewed the Open Skies Treaty in 1992 and 1993, Members
raised several concerns about the implications of the treaty for the United States. For
example, some were concerned that the costs of outfitting and operating the U.S.
Open Skies aircraft would outweigh the benefits that the United States would receive
by participating in the treaty. As a result, the Senate suggested that the United States
restrict its participation, conducting fewer than the 42 permitted observation flights
per year. Some were also concerned about potential risks to U.S. security from
observation flights that would gather information on U.S. military forces and
activities. If the Open Skies Treaty remains in force for many years, the United States
could host dozens of visits by other participants, with foreign military aircraft
equipped with sensors flying over U.S. territory. Virtually all observers agree,
however, that these flights will pose no security threat to the United States.
Introduction ................................................... 1
Background .................................................... 2
Key Provisions of the Treaty on Open Skies...........................3
Objectives ................................................. 3
Provisions Governing Observation Flights.........................4
Flight Distances and Airfields...............................4
Annual Quotas for Observation Flights............................6
Determining Passive and Active Quotas.......................7
Allocation of Observation Flights Among the Parties.............7
Passive and Active Quotas for the United States.................8
Current Status and Implementation Plans.............................11
Status of Treaty Ratification..................................11
Ratification by Other Parties...............................12
Planning for Implementation in the U.S...........................12
Open Skies Aircraft.....................................12
Trial and Training Flights.................................13
Implications for the United States..................................14
Value of Information........................................14
Conclusion ................................................... 16
List of Tables
Table 1. Parties to the Treaty on Open Skies..........................17
The Open Skies Treaty:
Observation Overflights of Military Activities
On March 24, 1992, the United States, Canada, and 22 European nations signed1
the Treaty on Open Skies. This Treaty had grown out of a May 1989 proposal by
President George Bush; he envisioned an agreement that would promote cooperation
and build confidence between the two Cold War blocs — NATO and the Warsaw
Pact. But the Warsaw Pact dissolved before the Treaty was completed, so it emerged
as an agreement among European nations, the United States and Canada (rather than
as a treaty between two opposing alliances). The Open Skies Treaty has not yet
entered into force, however, because Russia and Belarus have not ratified it.
Each of the parties to the Treaty on Open Skies will permit unarmed aircraft
operated by any other party to fly over its territory to observe military forces and
activities. By allowing the participants to gain insights and understanding into the
military capabilities of potential adversaries, the treaty can, according to its
supporters, build confidence, reduce the chances of military confrontation, and
encourage cooperation among the nations of Europe. Under the terms of the Treaty,
observation aircraft from the other participants can conduct up to 42 flights over U.S.
territory each year. (Russia, too, will be subject to 42 flights; the other participants
will host between 2 and 12 flights each year.) Consequently, if the Open Skies Treaty
remains in force for many years, the United States could host dozens of visits by other
participants. Virtually all observers agree that these flights will pose no security threat
to the United States. However, questions about the presence of foreign military
aircraft and the purpose of the observation flights may come up when the observation
This report provides basic information about the rationale for the Open Skies
Treaty, the provisions that govern its implementation, and the capabilities of the
aircraft and sensors that will be used during the observation flights. This information
can help Congress review the implementation of the treaty; it may also help Members
respond to concerns that constituents may raise about the presence of Open Skies
aircraft and observation flights around the country. The first section of this report
briefly reviews the history of negotiations on Open Skies. The second discusses key
provisions of the 1992 treaty. The third reviews the current status of the treaty and
1 The parties to the treaty are listed in the Table at the end of the report. The Text of the
Treaty can be found in U.S. Congress, Senate, Treaty on Open Skies, Message from the
President of the United States, Treaty Doc. 102-37, Washington, 1992.
The idea for a treaty on Open Skies first appeared in 1955, when President
Eisenhower suggested that the United States and Soviet Union permit aerial
observation flights over each other’s territories. In principle, aerial observation flights
would permit the two nations to reduce their reliance on worst-case estimates of the
other side’s military capabilities and to demonstrate that they were willing to
cooperate with each other to ease tensions. At the same time, in the era before the
development of observation satellites, aerial observation flights were only way for the
United States to gain needed intelligence information about military forces and
activities inside the Soviet Union. According to the Bush Administration, the
Eisenhower proposal “would have dramatically changed the quantity and quality of
our knowledge of the Soviet Union.”2 The Soviet leadership rejected President
Eisenhower’s proposal, arguing that the observation flights would simply legalize
President Bush revived the Open Skies concept in May 1989. At the time, as the
Cold War was ending, the United States believed increased transparency in Europe
would reduce the chances of military confrontation and build confidence. According
to Secretary of State James Baker, Open Skies “would promote and consolidate the
international trends towards openness already in train.”3 The Bush Administration
also viewed Open Skies as a test of Soviet willingness to move forward in a
cooperative relationship with the United States. According to President Bush, “Such
unprecedented territorial access would show the world the true meaning of the
concept of openness. The very Soviet willingness to embrace such a concept would4
reveal their commitment to change.”
Unlike the bilateral 1955 version of Open Skies, the negotiations that began in
February 1990 included all of the members of NATO and the Warsaw Pact.5 The
United States sought a pact-to-pact treaty, with the United States and NATO
conducting observation flights over the Soviet Union and Warsaw Pact nations, and
vice versa. However, as the negotiations proceeded, it became evident that the
Eastern European nations were not only unwilling to rely on Soviet technology to
2 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing,
3 U.S. Congress. Senate. The Treaty on Open Skies. Message from the President of the
United States, 102d Congress, 2nd Session. Washington, G.P.O., 1992. p. viii.
4 Remarks at the Texas A&M University Commencement Ceremony in College Station,
Texas, May 12, 1989. Weekly Compilation of Presidential Documents, v. 25, May 22, 1989.
5 The United States won the support of its NATO allies in consultations that began in August
Jonathan B. Back to the Future: The Open Skies Talks. Arms Control Today, v. 20, October
collect data, but were also interested in conducting their observation flights over
As a result, after the abortive Soviet coup in August 1991, the participants
altered their approach and produced a treaty among nations rather than a pact
between alliances. Each of the parties to the treaty can collect information about and
improve its understanding of the military forces and activities of any of the other
participants. As Secretary of State Baker indicated when the treaty was submitted to
the Senate, “The Treaty on Open Skies represents the widest-ranging international
effort to date to promote openness and transparency of military forces and activities.”7
But the treaty would do more than just build confidence and reduce the risk of
conflict. Many viewed the treaty as a symbol of the new Europe. According to
Thomas Graham, the acting Director of the Arms Control and Disarmament Agency,
“By strengthening the environment of security and confidence, such measures increase
the ability of our new partners in Europe to fill their commitments as participants in
the CSCE and to ensure that democratic change is irrevocable. They also facilitate
further security cooperation within a more stable and predictable international
Key Provisions of the Treaty on Open Skies
The primary objective of the Open Skies Treaty is to reduce the risk of conflict
by providing participants with the ability to collect information about the military
forces and activities of others in the treaty. In particular, “information derived from
Open Skies flights can contribute to participating states’ national efforts to address
a range of military and civil issues. These could involve observing known military
facilities and large-scale force deployments, determining the presence — but not the
detailed composition — of major military forces or large, possibly military-related
construction activities. As such, Open Skies flights could contribute to recognizing
the scope of excess military preparedness or unusual military activity.”9 This
information can help a nation make informed assessments about the military
capabilities of its neighbors, provide early warning of threatening military activities or,
conversely, information that could dispel concerns about ongoing military activities.
6 See the prepared statement of Ambassador John Hawes in U.S. Congress. Senate.
Committee on Foreign Relations. Treaty on Open Skies. Report 103-5, 103d Congress, 1st
Session. Washington, G.P.O., 1993. p. 157.
7 U.S. Congress. Senate. Treaty on Open Skies. Message from the President of the United
States. p. vii.
8 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report
9 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing,
Most observers agree that the Open Skies Treaty will add little to U.S.
knowledge of Russian military forces and activities and little to Russian knowledge
of U.S. or NATO forces and activities. The United States and Russia each operate
sophisticated observation satellites that can provide information without any
cooperation from the other side.10 Nonetheless, many have noted that the observation
flights will provide nations who do not have their own satellite systems with a way to
participate in the data collection and confidence-building process. As Ambassador
John Hawes, the U.S. representative to the Conference on Open Skies, noted, “the
treaty offers each of the participating states, regardless of size or level of
technological development, the opportunity for direct involvement in the observation
of military forces and activities of concern on the territory of other participating
states. For most of the participating states ... Open Skies will provide the first
opportunity they have had to acquire this kind of hard information relevant to their
Provisions Governing Observation Flights
Territorial Coverage. The parties to the Open Skies Treaty have agreed to
make all of their territory accessible to overflights by unarmed, fixed wing aircraft.
The only limitations on the flights would be those required for reasons of flight safety.
The United States and its NATO allies proposed unrestricted access for Open
Skies observation flights when the negotiations began. By the end of the first round
of negotiations in February 1990, the East European participants had agreed to this
proposal. The Soviet Union, on the other hand, sought to exclude large areas of its
territory from the observation flights for “national security reasons.” It also sought
to limit the duration of observation flights and to require that flights over some areas,
such as nuclear power plants and densely populated urban areas, occur at a minimum
altitude of 10,000 feet.12 When the negotiations resumed in November 1991 (after
the failed coup in Moscow), the Soviet Union announced that it would accept full
territorial coverage if flights over Soviet territory were conducted with Soviet aircraft
carrying Soviet sensors.13 This would allow Soviet officials to confirm that
observation aircraft were not carrying unauthorized sensors that could collect
sensitive information. Although the other participants preferred to use their own
aircraft in observation flights, they accepted this compromise.
Flight Distances and Airfields. According to the Treaty, to ensure that
observation flights cover the entire territory of participating nations, each party to the
10 In the arms control context, these satellites are known as “national technical means” of
11 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing,
September 22, 1992. p. 4.
12 For a description of the opening negotiating positions on Open Skies, see Tucker, Jonathan
B. Back to the Future: The Open Skies Talks. Arms Control Today, v. 20, October 1990.
13 See the prepared statement of Michael L. Moodie in U.S. Congress. Senate. Committee
on Foreign Relations. Treaty on Open Skies. Hearing, September 22, 1992. p. 9.
Treaty must specify the location of airfields that observation flights can originate from
and the maximum distance that flights from these airfields can travel. Every part of
the participant’s territory must be accessible to a flight that originates from one of the
airfields and travels no more than the specified maximum distance.
The United States has designated Travis Air Force Base in California, Elmendorf
Air Force Base in Alaska, Dulles International Airport outside Washington D.C. and
Lincoln Municipal Airport in Nebraska as its Open Skies airfields. The maximum
distance for flights originating at Travis and Elmendorf Air Force bases are 4,000
kilometers (2,455 miles) and 3,000 kilometers (1,841 miles), respectively. The
maximum distance for flights originating at Dulles and Lincoln Municipal airports are
Travis Air Force Base and Dulles International Airport will also serve as the Points
of Entry for Open Skies aircraft and crews that come to the United States for
inspections. All flights must land at these facilities first, even if they plan to conduct14
their observation flights from other Open Skies Airfields.
Time Lines. The Open Skies Treaty specifies that a nation seeking to conduct
an observation flight must inform the observed nation of its intentions 72 hours before
the observation team arrives at the Point of Entry (Dulles or Travis AFB, in the U.S.).
This notice is designed to ensure that the host country has enough time before the
observation begins to suspend any sensitive military exercises or activities that it
would not want observed during the flight. The observation flight can begin as soon
as 24 hours after the observation team arrives in the host country. Because the host
nation will not know precisely which areas will be covered by the observation flight
until the team arrives at the point of entry, it would not have enough time to conceal
large formations or concentrations of military forces in that area. The observation
flight must also conclude no longer than 96 hours after the team arrives at the Point
of Entry. This is designed to ensure that the visits do not disrupt exercises or
activities in the host country for an undue amount of time.
Mission Plans. The Treaty states that an observation team must present the
host with its mission plan when it arrives at the Point of Entry. This document
indicates what area of the host nation’s territory will be covered by the flight. It must
specify such details as the airfields the flight will use, the starting time and duration
of the flight, the distance the flight will travel, and a flight plan that specifies the route
and altitude for the flight.15 The host nation can propose changes to the mission plan,
for example, if weather conditions would affect flight safety, but it cannot deny the
observation team access to any area of its territory. The two parties must agree on
a plan within 8 hours of the time when the observation team arrives at the Point of
14 Open Skies aircraft can also land at Honolulu International airport, Malmstrom Air Force
Base, Phoenix-Sky Harbor Airport in Arizona, General Mitchell International in Wisconsin,
and McGhee Tyson airport in Tennessee if they need to refuel.
15 Thomson, David B. The Treaty on Open Skies. Briefing, Center for National Security
Studies, Los Alamos National Laboratory v. 5, July 1994. p. 15.
The Open Skies Treaty specifies that Open Skies observation flights will take
precedence over regular air traffic in the air traffic control system. If another aircraft
plans to fly along the same route at the same time as the Open Skies aircraft, the other
aircraft must alter its route. This is because a change in flight path or altitude of the
Open Skies aircraft could enhance or degrade the sensors operating on the aircraft
and, therefore, undermine the objectives of the observation flight.
The U.S. Federal Aviation Administration (FAA) has stated that giving
precedence to Open Skies aircraft will pose no threat or inconvenience to civil air
traffic in the United States.16 It frequently gives precedence to specified aircraft —
such as the President’s airplane, Air Force One — without passengers on other
aircraft knowing that their altitude or flight path has been altered. In addition, the Air
Force has concluded a formal agreement with the FAA that establishes a policy for
giving precedence to Open Skies flights. According to the Air Force, these policies
worked well during numerous Open Skies training and demonstration flights.17
The Open Skies Treaty contains several provisions to ensure that observation
flights do not pose an undue burden on the host nation. For example, nations can be
subject to only one observation flight at a time. This limit precludes both excessive
demands on the personnel who must implement the Open Skies provisions and an
unacceptable burden on national air traffic control system when it manages the flights
of the aircraft. The Treaty also specifies that an observation flight can not pass
repeatedly over the same spot or circle around a single area. This precludes efforts
to focus too much attention on a single facility or military activity.
Annual Quotas for Observation Flights
The Open Skies Treaty lists the number of flights that each nation must accept
over its territory each year — a passive quota. The passive quota is generally related
to the size of a nation’s territory. Each nation also has an active quota — a number
of flights that it can conduct each year. The Treaty specifies that no nation will be
allowed to conduct more flights over other nations’ territory than it is required to
receive over its own territory; i.e. the active quota for a nation cannot exceed the
passive quota for that nation. The Open Skies Consultative Commission (OSCC) is
charged with allocating the flights among the participating nations — i.e. each year
it prepares a list that specifies who will conduct flights over whom. The treaty states
that, when the OSCC allocates fights, no nation may conduct more than half of the
flights permitted by its active quota over the territory of one single party to the treaty
and no nation must receive a number of observation flights from a single nation that
equals more than half of the flights required by its passive quota.18
16 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies.
Hearing. p. 61.
17 Discussion with Air Force National Security Negotiations Division, October 18, 1995.
18 There is no requirement in the treaty for the actual number of flights conducted by a nation
to be equal to the number conducted over its territory. The actual number of flights will
depend on the requests of the other participants. If few participants seek flights over a
Determining Passive and Active Quotas. Prior to the Open Skies
negotiations, analysts in the U.S. Defense Department and the intelligence community
concluded that, with sufficient notice, the United States could host one observation
flight per week without putting sensitive military activities and facilities at risk.19
Hence, when the negotiations began in 1990, the United States indicated that it would
be willing to accept 52 observation flights per year over U.S. territory. Because the
Soviet Union had more than twice the land mass of the United States, the United
States proposed that the Soviet Union accept 110 observation flights per year. In
response, the Soviet Union proposed that each alliance — NATO and the Warsaw
Pact — host 30 flights per year, with no more than half the flights occurring over any
one nation in the alliance.
When the participants abandoned efforts to devise a treaty between the two
opposing alliances in late 1990, the United States accepted a NATO proposal to
allocate quotas for observation flights on a national basis. At that time, the United
States suggested that the Soviet Union accept 52 flights per year, as the United States
was willing to do. The Soviet Union refused, but it did raise the number of flights it
was willing to receive from 15 to 25. After the abortive coup in Moscow in 1991, the
Soviet Union agreed to accept 52 flights per year. After the December 1991 demise
of the Soviet Union, Russia stated that it would accept 40 flights per year, based on20
its relative size compared to the Soviet Union. The negotiators reached agreement
at 42 flights per year for the United States and Russia. (Russia has formed a group
with Belarus, so these 42 flights will cover both of those two nations.) The other
participants will receive between 4 and 12 flights per year, depending on the size of
Allocation of Observation Flights Among the Parties. Open Skies
observation flights will be allocated on an annual basis by the Open Skies Consultative
Commission (OSCC). Each of the parties to the treaty will submit a list of the
observation flights it wishes to conduct during the coming year. If the parties request
more flights over a particular nation than allowed by that nation’s passive quota, the
OSCC will divide the number of permitted flights among the requesting parties. As
a result, all participants may not be able to conduct all of their requested flights. At
the same time, the treaty permits two or more nations to join together on observation
flights and essentially “share” the passive quota of observed nation. This will allow
nations to participate in more observation flights without exceeding the passive quota
of the observed nation. In addition, all parties to the Open Skies Treaty can purchase
data collected during any nation’s observation flights. Hence, all nations will have
access to information about the other parties’ military forces and activities, even if
they do not conduct their own observation flights.
nation’s territory, so that its passive quota is not filled, that nation can still conduct the full
number of flights permitted by its active quota.
19 Tucker, Back To the Future: The Open Skies Talks, p. 21.
20 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies.
Hearings. p. 40.
Passive and Active Quotas for the United States. The Open Skies Treaty
gives the United States a passive quota, and therefore, an active quota, of 42
observation flights per year. These are the maximum number of flights the United
States could conduct or receive each year. However, when nations requested flights
for the first year of treaty implementation, only one party to the treaty — the group
of Russia and Belarus — requested flights over the United States. And this group
requested only 4 flights over the United States. The United States submitted a
request for its maximum permitted number of flights over other parties, but it
requested flights over many of the same nations that other participants wanted to visit.
As a result, when the OSCC allocated flights for the first year of treaty
implementation, the United States received only 8 flights — over Russia and Belarus.
It will also conduct one flight jointly with Canada over Ukraine. Because the OSCC
will reallocate flights each year that the treaty remains in force, the United States may
be granted a greater number of its requested flights in future years.
The Open Skies Treaty specifies that observation flights must be conducted by
unarmed, fixed-wing aircraft. These aircraft can be provided by either the observing
party or the observed party, if the observed party requests to use its own plane. The
parties cannot use helicopters for their observation flights.
During the negotiations, the United States and NATO proposed that the nation
conducting the observation flight provide the aircraft for the flight. The Soviet Union,
on the other hand, proposed that the nation hosting the observation flight provide its
own aircraft, or that all nations rely on the same fleet of dedicated Open Skies
aircraft.21 This proposal reflected Soviet concerns about the quality of data that could
be collected by aircraft using Western sensor technologies and Soviet concerns about
the possible presence of illicit sensors on observation aircraft. The participants from
Eastern Europe also sought a common pool of aircraft because they did not want to
rely on Soviet technology for the observation flights. The United States and NATO
argued, however, that a common pool of aircraft would be costly and difficult to
maintain. Nonetheless, they agreed that the Soviet Union could provide its own
aircraft for flights over Soviet territory in exchange for Soviet agreement to open all
its territory to observation flights. In addition, nations can borrow or lease aircraft
from other parties to the treaty so that all parties can conduct Open Skies observation
flights even if they cannot afford their own aircraft.
U.S. Aircraft. The United States is planning to equip 3 aircraft specifically for
Open Skies observation flights. The first is already operational; it is based at Offut
Air Force base in Nebraska and is used to conduct testing and training flights for
Open Skies personnel. Once the treaty enters into force, this aircraft will be used for
training flights and as a backup aircraft for observation flights. The other two aircraft
were reached full operational capability during 1996, one by the middle of the year
and the second by the end of the year.
21 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies.
Hearing. p. 42.
Open Skies aircraft can be equipped with four types of sensors: optical
panoramic and framing cameras (cameras for still photography) with a ground
resolution of 30 centimeters (around 1 foot); video cameras with a ground resolution
of 30 centimeters (around 1 foot); infrared line-scanning devices with a ground
resolution of 50 centimeters (around 20 inches); and sideways-looking synthetic
aperture radars (SARs) with a ground resolution of 3 meters (around 8 feet).
According to U.S. officials, these sensors will be able “to recognize major pieces of
military equipment. This has been characterized, for example, as the ability to tell the
difference between a tank and a truck... This level of capability is not sufficiently
detailed to reveal technical information about the major items of equipment, nor
would it permit identification of particular models of a category of equipment in most
The United States and NATO initially proposed that the Open Skies Treaty
impose no restrictions on the capabilities of the Open Skies sensors, with the
exception of a ban on “signals intelligence” sensors that could eavesdrop on electronic23
communications. The sensors that NATO wanted to employ — including still and
video cameras, infrared line scanning devices, synthetic aperture radars, spectrometers
and air-sampling devices — would have permitted the collection of both photographic
data on visible activities and scientific data on activities inside facilities (such as the
manufacture of chemical agents). The Soviet Union, on the other hand, wanted the
treaty to permit only optical cameras. The United States, NATO, and Eastern
European participants rejected the Soviet approach because it would have severely
limited the quantity and quality of information collected during the observation flights.
The Soviet Union eventually agreed that the participants could use infrared sensors
and synthetic aperture radars; in exchange, NATO dropped its proposal for the use
of a wider variety of sensors.24
During the negotiations, the participants also disagreed about the resolution that
would be permitted on the sensors and determining the level of detail the data would
show. NATO proposed that optical cameras provide a ground resolution of 7.5
centimeters (about 3 inches); the Soviet Union suggested 30 centimeters (about 125
foot). For the synthetic aperture radar, NATO sought a resolution of 3 meters
(about 8 feet); the Soviet Union suggested 10 meters (about 30 feet). The two sides
22 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies.
Hearing. p. 44.
23 Tucker, Back to the Future: The Open Skies Talks, Arms Control Today, v. 20, October
24 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies.
Hearing. p. 41.
25 A synthetic aperture radar is capable of looking “around” clouds and, therefore, can collect
data regardless of weather conditions on the ground.
eventually agreed to use the Soviet proposal for optical cameras and the NATO
proposal for SARs.26
Sensor Quality. The Open Skies Treaty specifies the sensors must be derived
from “off-the-shelf” technology available to all the parties. This responds to the
Eastern European nations’ concerns about being at a disadvantage if they had to rely
on Russian technology for their data collection. Off-the-shelf sensors may collect a
lower quality of data than the state-of-the-art technologies NATO had hoped to use.
At the same time, the use of off-the-shelf technology made it possible for all nations
to share the data collected by any nation during an observation flight.
The treaty contains a provision that allows the parties to approve the use of
improved sensors and additional types of sensors on observation flights. This
provision not only allows the participants to take advantage of technological
advances, but would allow them to expand the objectives of the treaty into areas such
as monitoring air quality for environmental protection. The Open Skies Consultative
Commission would have to approve proposals for new sensors; if any participant
objected, the sensors would not be used.
The treaty contains several provisions to address concerns about the possible
presence of unauthorized sensors on board Open Skies Aircraft. First, at Russian
insistence, the treaty permits any nation to request that its own aircraft be used for
observation flights. Second, the treaty permits the nation hosting the observation
flight to fully inspect the observing nation’s aircraft to ensure that it does not carry
covert sensors and to conduct calibration exercises to ensure that sensors do not have
capabilities in excess of those permitted by the treaty. Finally, when the nation
conducting the observation flight prepares its mission plan, it must make sure that the
aircraft’s altitude throughout the flight, when combined with the calibration of the
sensors, is consistent with the limits on sensor resolution; cameras would have better
resolution if the aircraft flew closer to the ground.
The original 25 signatories of the Open Skies Treaty include all of the members
of NATO and the former Warsaw Pact, along with Russia, Ukraine, and Belarus from
the former Soviet Union. The other newly independent states from the former Soviet
Union, including the Baltic states, can join the pact at any time; Georgia and
Kyrgyzstan have already done so. All other European nations who are members of
the Organization on Security and Cooperation in Europe can apply to join the treaty
during the first six months after the treaty enters into force.
The Open Skies treaty also contains provisions to expand beyond Europe, the
United States, and Canada. After the treaty has been in force for six months, the
Open Skies Consultative Commission can consider a request to join from any other
nation that it considers able to contribute to the objectives of the treaty. Because the
26 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing.
OSCC must make its decisions by consensus, a nation’s application to join the treaty
will be rejected if any one of the current participants objects.
Current Status and Implementation Plans
Status of Treaty Ratification
U.S. Ratification. President Bush presented the Open Skies Treaty to the
United States Senate on August 12, 1992. The Senate Foreign Relations Committee
held hearings on the Treaty in September 1992 and March 1993. The Senate Armed
Services and Intelligence Committees also reviewed the treaty. The full Senate gave
its consent to ratification of the Treaty in August 1993. The United States officially
ratified the treaty on November 3, 1993.
In their reports, the three Senate committees that reviewed the treaty highlighted
several concerns about the costs of implementation and the possible implications for
U.S. security. All three were concerned about the cost of a fleet of three fully-
equipped aircraft, which the Department of Defense believed it needed to conduct all
42 observation flights each year. The committees noted that the United States would
collect little new information during these flights and, therefore, might not need to
conduct 42 flights.27 The committees also expressed concerns about the addition of
new sensors to Open Skies aircraft; they noted that these sensors might not only add
to the costs of Open Skies implementation but might also eventually put U.S. national
security at risk.28
The Senate attached two conditions to its resolution of ratification for the Open
Skies Treaty. First, the Senate found that “United States interests may not require the
utilization of the full quota of allowed observation flights or the procurement of more
than one or two observation aircraft.”29 As a result, the Senate called on the President
to submit a report after the first year of treaty implementation that reviewed the
operation of the Treaty and provided an analysis estimating the number of annual
observation flights and aircraft that the United States would need for the duration of
the Treaty. Second, the resolution stated that the President should provide the Senate
with prompt notification of proposed improvements to Open Skies sensors and should
not provide U.S. approval to the proposed changes until 30 days after the Senate
received the notification.30 This time period would presumably be used to assess the
costs of the new sensors and possible implications for U.S. security.
27 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report
28 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report
29 The Resolution of Ratification in reprinted in Congressional Record, v. 139, August 2,
30 Congressional Record, v. 139, August 2, 1993. p. S10106.
Ratification by Other Parties. The Open Skies Treaty has been ratified by all
the participants except Russia, Belarus and Kyrgyzstan. The Ukrainian parliament
voted on the treaty three times without reaching consensus, but eventually did so and
Ukraine ratified the treaty on March 2, 2000. Reports indicate that the delay in these
nations can be attributed to their concerns about the cost of implementation. Each of
these nations is facing economic difficulties. Officials in Russia, Ukraine, and Belarus
have complained about the costs of implementing arms control agreements, such as
the Strategic Arms Reduction Treaty (START I) and the Conventional Armed Forces
in Europe Treaty (CFE). The treaty cannot enter into force until Russia and Belarus
approve its ratification.
Planning for Implementation in the U.S.
Interagency Participation. Policy decisions affecting the implementation of the
Open Skies Treaty will be addressed in an interagency committee with representatives
from the Department of Defense, the Department of State, and the intelligence
community.31 This group will address questions about a number of issues, including
the number of observation flights the United States should request over specific
nations and the areas of those nations that should be covered by each flight.
The United States Air Force and the On-Site Inspection Agency (OSIA), which
is now a part of the Defense Threat Reduction Agency, will take the lead in
implementing Open Skies observation flights for the United States. The Air Force
will own, operate, and maintain the U.S. Open Skies Aircraft. Representatives from
OSIA will operate the sensors during U.S. observation flights and participate as
escorts and observers in observation flights other nations conduct over U.S. territory.
Open Skies Aircraft. The United States had initially planned to deploy 3 fully
operational observation aircraft to support 42 observation flights per year. However,
in response to congressional concerns about the cost of these aircraft, the Air Force
now plans to outfit only two aircraft with the full suite of sensors needed to conduct
observation flights. The third aircraft, which is currently conducting testing and
training flights for Open Skies personnel, is equipped with only the optical cameras
permitted by the treaty. It will not be modified to carry the infrared sensor or
synthetic aperture radar.
The United States Air Force, which will operate the Open Skies Aircraft, is
modifying existing C-135 airplanes for the Open Skies mission. Similar in size to
civilian 707 aircraft, these modified OC-135 airplanes will seat 38 people, including
the Air Force flight crew and maintenance crew, representatives from the country that
is hosting the U.S. observation flight, and crew members from the On-site Inspection
Agency who will help with mission planning and operate the aircraft’s sensors.
Because the Air Force has decided to modify existing aircraft, there will be no
expense associated with the purchase of new aircraft. Nonetheless, the Air Force is
spending around $62 million to equip the aircraft with sensors and other equipment
needed for Open Skies observation flights. It also plans to spend an additional $7.3
31 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing.
million on research and development for new sensors and integration of sensors and
Trial and Training Flights. The United States has participated in more than
50 training and trial flights since 1993. Crews assigned to the aircraft at Offut Air
Force Base conduct, on average, two training flights per month to maintain their
proficiency in operating the aircraft. U.S. crews have also participated in trial flights
to certify that the aircraft and sensors operate in accordance with U.S. and treaty
requirements and to support ongoing OSCC discussions about procedures that will
be used during official observation flights.32
The United States has also conducted several flights in cooperation with other
parties to the treaty. These flights carry participants from both nations and are used
to test the procedures for mission planning and mission implementation. In June
1998, the United States conducted training flights over Ukraine. This effort was
designed not only to exercise U.S. mission procedures, but also to demonstrate these
procedures to officials in Ukraine, in part to show that these procedures would not
be too costly or intrusive to implement.
Other treaty signatories have also conducted trial inspection flights. For
example, in June 1995, the German Open Skies aircraft conducted trial flights over
U.S. territory. This was the first time that a foreign military aircraft had ever had33
unrestricted access to U.S. airspace. Russia has also conducted a training mission
over the United States, with its aircraft visiting U.S. territory during August 1997.
Russia also conducted a training flight over Bulgaria in April 1998, and hosted a
training flight over Russian territory in August 1998. The German crew used a
Russian aircraft for its observation flight. In July 1998, Germany had announced that
it would no longer use its own aircraft to participate in Open Skies flights.34 The first
aircraft that it modified for this purpose had crashed in 1997 and it suspended plans
to modify a second aircraft. Analysts were uncertain as to whether the German
decision would affect the ratification and implementation of the Open Skies Treaty.
When the treaty enters into force, the Department of Defense has estimated that
it might cost the United States $20-25 million per year to conduct and host
observation flights. Some have estimated that it could cost the United States
$25,000-$35,000 to host an Open Skies observation flight and $165,000-$170,00035
to conduct an observation flight using the U.S. aircraft. These are primarily the
costs of training and employing the personnel needed to operate the aircraft and the
sensors and the actual costs of flying the aircraft.
32 Discussions with the Air Force National Security Negotiations Branch, October, 18, 1995.
33 Information provided by the On-site Inspection Agency, October 20, 1995.
34 Defense Ministry Withdraws from Control Flights. Main Frankfurter Allegemeine. July
35 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report,
Implications for the United States
Most analysts and observers agree that the Open Skies Treaty can play a valuable
role as a confidence building measure among the nations of NATO and the former
Warsaw Pact. At the same time, some have questioned U.S. participation in the Open
Skies regime. These questions have focused on two key areas: the value of the
information the United States might collect during Open Skies observation flights and
the cost to U.S. security of the information that others might collect during flights
over U.S. territory.
Value of Information
Several analysts and some Members of Congress have noted that the United
States does not need to bear the costs of equipping and operating Open Skies aircraft
to acquire information about the military forces and activities of other nations. It
already operates expensive photo reconnaissance satellites that serve the same
purpose. Some have proposed, therefore, that the United States conduct few
observation flights and limit its participation in the treaty.36
Most supporters of the Open Skies regime have acknowledged that the United
States will not acquire much new information during its Open Skies observation
flights. Nonetheless, as Ambassador John Hawes, the U.S. representative to the Open
Skies Conference, noted during his testimony before the Senate Foreign Relations
For most of the other participants, however, the ability to utilize the Open Skies
sensor suite to observe the full territory of the other participating countries will
represent a new and very significant enhancement in their ability to gather security-
related information. The United States will ... be a major indirect beneficiary of37
this increase in knowledge, confidence, and security of the participants.
The treaty’s supporters have also noted that the United States might acquire
information during Open Skies observation flights that is more useful than satellite
data for international relations purposes. For example, the United States is often wary
of releasing satellite photographs that could reveal secret information about U.S.
satellite capabilities. But similar information acquired during Open Skies flights could
be used in the international arena.38
36 This point is made in the report of the Senate Select Committee on Intelligence. See U.S.
Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report 103-5.
37 U.S. Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Report
38 See the prepared statement of Thomas Karas, Office of Technology Assessment, in U.S.
Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing. p. 35.
Although most analysts acknowledge that Russia, like the United States, does
not need to participate in the Open Skies Treaty to collect information about military
forces and activities in the United States, some have expressed concerns that nations
who currently lack access to satellite data could use Open Skies observation flights
to collect sensitive information about the U.S. military or U.S. industry. Some have
also expressed concern about the possibility that treaty participants could transfer
information collected during Open Skies observation flights to others, including rogue
nations or terrorists, who might use the information in planning operations against the
United States. These concerns would be heightened if the Open Skies regime allowed
the use of more sophisticated sensors or if the treaty were expanded to permit
participation by nations who remain hostile to the United States.
Officials from both the Bush and Clinton Administrations insisted during
testimony before the Senate Foreign Relations Committee that information collected
during Open Skies flights would not place U.S. national security at risk.39 A number
of factors would limit these nations’ ability to collect sensitive information. For
example, the treaty requires advance notice before flights begin and prohibits flights
from circling or returning to a specific area repeatedly during the flight.40 The
advance notice would allow the United States to cease any sensitive activities before
an observation flight began. The ban on repeat visits during a single flight would
complicate an observing nation’s effort to focus extra attention on a single facility or
U.S. officials have also emphasized that the resolution of sensors permitted by
the Open Skies Treaty will not be sufficient to allow the collection of sensitive
intelligence about U.S. military forces and activities.41 The sensors will lack the
capability to identify the capabilities of weapons systems or the types of activities
occurring in closed structures. In addition, information about the size and location
of most major military installations in the United States is already available to the
public at large. Because the Open Skies observation flights would not provide any
additional information about activities occurring inside buildings, the flights would do
little to help those seeking targets for attack in the United States. Finally, it is
unlikely that the Open Skies Treaty would expand to include any nation that might use
Open Skies data to threaten a current participant. The Open Skies Consultative
Commission must approve all applications for admission. The treaty states that, if
39 According to Brig. Gen. Teddy E. Rhinebarger, who represented the Joint Chiefs of Staff
at the Senate hearings, “... the scope of the Open Skies regime was carefully considered, and
the overflight access Open Skies provides does not place sensitive facilities at risk.” see U.S.
Congress. Senate. Committee on Foreign Relations. Treaty on Open Skies. Hearing. p. 16.
40 See the prepared statement of Thomas Karas in U.S. Congress. Senate. Committee on
Foreign Relations. Treaty on Open Skies. Hearing. p. 33.
41 “The resolution limit of 30 centimeters for optical sensors establishes a level of
intrusiveness commensurate with the Treaty’s goal of openness and transparency in military
forces and activities while effectively safeguarding legitimate national security interests.” See
U.S. Congress, Senate, Committee on Foreign Relations, Treaty on Open Skies, Hearing. p.
any one of the current parties to the treaty objects to an applicant, the OSCC would
have to reject the application.
The primary benefits of the Open Skies Treaty will accrue to its European
participants. These nations will not only be able to acquire information about military
forces and activities in neighboring nations, they will also be able to collect this
information themselves, without relying on the observation satellites of other nations.
Some observers believe the United States should limit its participation in the
Open Skies regime to reduce the costs of equipping and operating observation
aircraft. However, even if the United States reduces its own participation, it must
remain willing to host up to 42 observation flights from other countries each year. If
the first year’s plans are any indication, this should not create an undue burden; only
Russia and Belarus showed an interest in conducting flights over U.S. territory and
they only requested 4 flights.
Still, if the Open Skies Treaty remains in force for many years, the United States
could host dozens of visits by other participants, with foreign military aircraft
equipped with sensors flying over U.S. territory. Virtually all observers agree that
these flights will pose no security threat to the United States.
Table 1. Parties to the Treaty on Open Skies
NATO MembersEastern European Participants
CanadaCzech Republic (a)
ItalySlovak Republic (a)
(a)The Czech and Slovak Republics each signed after they separated on Jan. 1, 1993.
(b)Georgia signed in 1992.
(c)Kyrgyzstan signed in February 1993.